Photodynamic Therapy (PDT) is a photochemistry based approach to the treatment of disease and relies on the use of light to activate certain non-toxic chemicals called photosensitizers. An attribute of PDT is its dual selectivity conferred by the localization of the photosensitizers and the spatial confinement of light. PDT is approved by regulatory authorities world-wide for a number of cancer and non-cancer applications and continues to emerge as a potential therapeutic modality for a variety of new indications. Because of the ability of most of the PDT agents to fluoresce, advances in optical diagnostic and therapy monitoring modalities have also evolved rapidly and online monitoring and therapy approaches are being developed. The 13th Congress of the International Photodynamic Association Conference will be held in Seattle (11- 15 June 2009) and is expected to attract physicians and scientists from the world over and is aimed at being forward-looking, projecting areas most amenable to Photodynamic Therapy as well as capturing the current status of the field. Both basis science and clinical topics will be covered allowing adequate times for discussion. The conference should be useful to those already in the field of PDT and also to those contemplating entering it. This is anticipated to be a particularly good forum for exchange of ideas between laboratory scientists and clinicians. Of particular interest to the association is the attendance by students and postdoctoral fellows and effort is being made to provide funding for these young scientists to defray some of the conference costs. Public Health Relevance: This conference is designed to improve public health by providing a format for investigators to exchange information in an emerging procedure for cancer detection and treatment. The use of fluorescent agents that localize at tumor sites facilitates diagnosis. The ability of these agents to cause a highly-selective form of cell damage upon irradiation with visible light can be utilized in cancer treatment procedures.